A teenage boy and a woman have been charged, and a third woman is in custody after two paramedics were allegedly assaulted and their ambulance was rammed as they went to the aid of a patient in Melbourne's north.

One ambulance officer underwent surgery after the alleged attack at Hobbs Crescent in Reservoir at about 6:30pm on Thursday.

Police arrested the 15-year-old boy at about 1:00pm on Friday at Banksia Street in Ivanhoe.

The paramedics were trying to care for a disoriented elderly man when three bystanders allegedly became aggressive.

One paramedic suffered a suspected broken foot, cuts and bruises after he waskicked, punched and repeatedly knocked to the ground by a man and two women.

Police allege another paramedic was struck on the head when she went to the aid of her colleague.

The attackers allegedly then got into their car and rammed the ambulance before speeding from the scene.

The teenager was charged on Friday afternoon with intentionally causing serious injury, serious assault of an emergency service worker and other assault-related offences.

A 30-year-old Epping woman handed herself in to the Reservoir Police Station at about 4.00pm before being charged on the same evening.

She is also facing charges relating to the serious assault of an emergency service worker, as well as theft and traffic-related offences.

Police said an 18-year-old woman from Reservoir also handed herself in to the Preston Police Station at 7:00pm.

The boy and the Epping woman will appear before an after-hours bail justice on Friday evening where police will oppose bail.